1. Field of the Invention
The present invention relates to a pretension loading method for a power transmission chain used in a power transmission apparatus such as a chain type continuously variable transmission that is applied to a vehicle etc. and a pretension loading apparatus that is used for the method.
2. Related Art
As a continuously variable transmission (CVT) of an automobile, for example, there is a known continuously variable transmission including an input pulley which is disposed in an engine, an output pulley which is disposed in a drive wheel, and a power transmission chain with a continuous shape which is wound around both the pulleys. In the power transmission chain, a pin and a strip serving as pin members are inserted through a pin hole disposed in a link plate. At this time, sheave surfaces with a conical shape of both the pulleys come into contact with, for example, a pin end surface of the chain to thereby generate a friction force, so that a power is transmitted by the friction force.
At the time of manufacturing a power transmission chain including the link plate and the pin members, a plurality of link plates having a pair of pin holes are laminated so that the pin holes communicate with each other. Subsequently, the pin is inserted through the communicating pin holes, so that the plurality of link plates are bendably connected to each other to thereby configure a chain with an endless loop shape. Subsequently, pretension is loaded on the chain with an endless loop shape, so that the length or the pitch of the chain made uniform (for example, see JP-A-8-74938 and JP-A-11-201238).
In order to load pretension on the chain with an endless loop shape described above, generally, the chain is wound around two rollers which are disposed at a predetermined gap therebetween, and then the rollers endlessly rotate the chain so as to load a tensile load thereon. An example of chain deformation due to the load tension includes an elastic deformation and a plastic deformation. In general, the tensile load is controlled to be a predetermined value on the basis of the magnitude of the tensile load as a reference, so as to load pretension on the chain. For this reason, it takes time to obtain a standard length of chain.